Electroluminescent semiconductor devices, such as lasers, are presently used in a variety of communications, recording, and detection systems. In each application, it is important that the light emitted from the device be accurately aligned with, or coupled into, other components of the system, such as an optical fiber. A primary limitation on the effectiveness of such a system is the coupling efficiency, i.e., the amount of light emitted by the electroluminescent device compared to the amount of light which is detected at the other end of the fiber.
An important parameter for coupling is consideration of the dimensions involved. For instance, the emitting facet of a typical laser device is about 250 microns in width, but the "lasing spot" (the location on the facet from which the light actually is emitted) for a multimode laser device is only about 10 microns in width. The same 250 micron wide facet of a single mode laser has a lasing spot only 2 to 3 microns in width. The light from the "lasing spots" must be coupled into a 50 micron or an 8 to 10 micron diameter fiber core respectively. Thus, in the assembly of an optical communications system, misalignment of the laser device by only several microns becomes a problem. Therefore in connecting a laser device into a system, it is important to know the location of the lasing spot on the facet exactly. This is not always easy. For instance, many lasers include a stripe contact. This, to some extent, dictates where the light emission will occur, but the light emission may occur several microns to one side or the other of the stripe contact. Further, when laser devices are mounted "striped side down" onto a copper heatsink, the exact location of the stripe is not known.
It would be desirable, therefore, to develop a method of mounting laser devices onto heatsinks such that in subsequent connection of these devices into systems, the lasing spot on the emitting facet can be readily located to provide efficient alignment of the device with respect to other components of the system.